Flint tools sometimes show signs of
having been used extensively, in the form of smooth patches, a feature
known as 'use wear', sometimes also called 'sickle gloss'. In
recent decades this aspect of flint tools has become a subject of study
in its own right and can be very revealing.

Use wear shows as shiny or glossy patches on the working edges, and
sometimes on other parts of a tool. It is typically caused by the
repetitive scraping of leather hides to make them suitable for clothes
or shelter, or by repeated use in cutting wood or vegetation. Because
flint is very hard (close behind diamond on the mineral hardness scale)
it takes a great deal of wear to abrade the surface, creating a glossy
patch. Use wear could thus indicate a favoured tool, or one that is 'curated'
(kept and carried from place to place) or perhaps one that is communally
used.

In the first photo, shown right, a Mesolithic end scraper has been
polished to a significant degree by continual use - probably on leather
hides.

In one unusual case, illustrated right, there is very significant use
wear over the base of a fist-sized worked flint that appears to have been used in some
'smoothing' or 'flattening' role over a wide area, perhaps in preparing
leather hides, or possibly in grinding seeds.

In another case, use wear can be seen as twin patches on flat
facets angled to each other, suggesting the tool was rubbed repeatedly
along a narrow cylinder, such as an arrow or spear shaft.

In a few very rare cases, it has proved possible for DNA to be
recovered from the edges of flints, identifying the animals whose
remains were cut up and skinned with their aid.